1. Field of the Invention
The invention of this application is within the field of hazardous bulk material handling equipment and intermodal materials transfer equipment.
2. General Discussion of the Background
The transportation of coal provides several unique problems not encountered with other bulk commodities. Principal among these problems is the fact that coal, while it is a solid product, is a flammable material. When stored in bulk quantities, it is susceptible to the development of spontaneous combustion, and this tendency is increased if the coal becomes moistened. Gradual temperature rises occur within stored wet coal, and can reach a point, if the quantity of coal is great enough, that the coal will actually catch fire.
This problem is made worse by the fact that coal is a bulk commodity, for which transportation costs are a major portion of the overall economic cost of the use of the product. Thus, coal is often shipped by waterborn commerce, an environment maximizing the problem of moisture and in which large bulk quantities are often accumulated, producing significant combustion hazards.
Coal is a naturally mined product, occuring in a wide variety of grades related to its overall cleanliness, sulphur content, foreign material content (especially shale), and other characteristics having a bearing on the value of the coal for various purposes and thus on its price. As a result, coal is brought to certain quality specifications, depending upon its end use.
Since the coal provided from various mining sources in general either exceeds or falls below the desired quality requirements, it is necessary to blend various coals in order to achieve an overall mixture having the desired properties.
As it is customary that coal is shipped from individual mines in barge load lots, a barge load is typically of a particular quality. This coal is sampled, stored and blended to specification at an intermediate handling facility, usually located for convenience at the point at which the coal is removed from barge or river traffic and transferred to ocean going vessels.
Such shore side facilities are by the nature of the commerce very large, consuming sizeable areas of relatively scarce waterfront land, and imposing significant environmental impact. In addition, the fact that the coal must be transferred from river traffic to ocean going traffic at a fixed location creates major scheduling and access problems as both the barges and the ocean going vessels must be brought to a specific location.